Saponification of cellulose esters



Patented Mar. 29, 1938 2,112,275

UNITED STATES OFFICE SAPONIFICATION F CELLUILOSE ESTERS Henry Dreyfus,London, England No Drawing. Application January 4, 1935, Se-

rial No. 327. In Great Britain January 15, 1934 8 Claims. (Cl. 8-20)This invention relates to improvements in the adjusted so as to producerapid saponification, or

treatment of filaments, threads, yarns, fabrics the type of process inwhich the material underand the like and is more particularly concernedgoing treatment is first impregnated with the apwith processes for thesaponification of textile and propriate. amount of saponifying agent,for exother materials containing cellulose esters. ample in a bath or ina padding mangle or like I have found that it is of advantage in theimpregnating machine andis subsequently heated,

saponification of materials of the type referred for example by passageover heated drums or to above, particularly when using stronglyalkaother heated surfaces to effect a rapid saponificaline saponilyingagents such for example as caustion. Similarly spinning box cakes, yarnwound 1o tic soda, to have present a small quantity of a on perforatedbobbins or other foraminous suplo salt of the saponifying agent wtih anaromatic port may have the saponil'ying medium circulated substance ofweakly acid reaction. Thus for ex-. through them. Travelling materialsare preferample it is of advantage when saponifying such ably treated inwarp formation, that is to say a materials by means of caustic soda tohave present large number of yarns, threads or the like are smallquantities of the sodium salt of phenol, aligned and carried togetherthrough the saponil5 salicylic acid, benzoic acid or other phenol orlying treatment with the aid of rollers or other aromatic carboxylicacid. In the presence of driving means operating upon the sheet of yarnssmall quantities of such substances saponification as a whole. In thisWay great uniformity of can be carried out rapidly Without damaging thetreatment can be obtained with resultant unimaterials or undesirablyreducing their tenacity formity in the properties, and particularly inthe or extensibility. dyeing properties of the materials treated.

The term phenols is intended to include not The invention includes'bothpartial and comonly phenol itself and its homologues such as pletesaponification. For example in the case of cresol, but in addition diandpolyhydric phenols treating cellulose acetate materials the saponiforexample resorcinol, pyrocatechin, hydroquification may be such as toremove 10-20 or 30% none, phloroglucinol, pyrogallol and the like and ofthe original acidyl content of the ester and may substitution productsof the phenolic bodies and be for the purpose of increasing the safeironing especially carboxy substitution products such as point of thematerials or generally increasing salicylic acid. The carboxysubstitution products their resistance to heat treatments and/or forapp-ear to give better results qua the textile propthe purpose ofconferring thereon an affinity for erties of the saponified materialsthan the simple cotton colours, or may be such as to remove a phenols.much greater proportion of the original acidyl The saponifying agentpreferably comprises an content such as 50-70 or 75%, or to producecomaqueous solution of caustic soda or caustic potash. pletesaponification.

The solution may be of relatively low concentra- As indicated above thephenol or equivalent 5 tion, for instance from 1 or 2% or even less to 3or substance or sodium phenate or other reaction 4%, or of considerablyhigher concentration, for product of the substance with the saponifyinginstance 5-10 or 15%. The bath may be at atmedium is preferablyincorporated directly in an mospheric temperature or below atmosphericbut aqueous solution of caustic alkali or other alkao for rapidsaponification somewhat higher temperline substance so as to make up thesaponifying 40 atures are preferable and the bath may even be medium.However, the yarns, threads, fabrics maintained at a temperature justshort of the or other materials may if desired be impregnated boilingpoint. with the phenol or phenate prior to contact with The phenol orits equivalent is preferably disthe saponifying medium. In order toobtain a -15 solved in the saponifying medium, although othgoodimpregnation the phenolic substance may be er suitable methods ofapplication are not exapplied in the free state rather than in the formeluded. The phenol or the like should be present :of a phenate. In sucha preliminary impregnain'small' quantity, for example in a concentrationtion care should be taken that the concentration of the order of0.2-0.5% up to 1% based on the of the phenol in the pretreatment bathdoes not total saponifying medium. produce incipient solution of thecellulose ester The saponifying medium may be applied in any unless atthe same time mutual adherence of fllasuitable manner. The inventionincludes simple ments to make for example a monofil or ribbon istreatments of hanks or other packages in a bath, desired. the treatmentof travelling filaments in which The saponifying medium may contain inaddicase the saponifying conditions are preferably tion to thesaponifying agent and the phenolic 56 susbtance any other desiredconstituents, as for example swelling agents for the cellulose esterunder treatment. For example, when cellulose acetate materials aretreated the saponifying medium may contain ethylene methylene ether,dioxane or acetone.

The following example illustrates the invention:

Example Cellulose acetate yarn is drawn from a creel in warp formationthrough a saponifying bath, through a washing bath which removesresidual alkali carried over from the saponifying bath, and over aseries of steam heated drying rolls to suitable collecting means. Thesaponifying bath contains an aqueous solution of caustic soda ofrelatively low concentration, in which is dissolved a small quantity ofsodium phenate.

Instead of phenol, other like acting substances may be employed, forexample resorcinol, phloroglucinol or salicylic acid.

The process of the invention is particularly applicable to the treatmentof cellulose acetate materials but may be applied to other organicesters of cellulose, for example cellulose formate, propionate,butyrate, oxy-ethyl acetate and the like. The tensile strength of theresulting products may be improved by stretching the materials,preferably before the saponifying treatment and either during or afterthe spinning of the materials, for example stretching them under theaction of a softening agent, for instance the solvents mentioned above,to 200 to 300 or even 500% or more of their original length.Furthermore,

'it is advantageous to employ cellulose esters of high viscositycharacteristics, for example, in the case of cellulose acetate, productshaving a viscosity of above 40 and preferably more than 50 to 100 oreven 200 or more as measured by a comparison of the viscosity of a 6%solution of the cellulose acetate in acetone against that of rglycerin'e taken as a standard of 100.

What I claim and desire to secure by Letters Patent is:-

1. Process of saponifying filaments, threads,

' ribbons and like materials composed substantially of organic esters ofcellulose comprising treating the same with a bath containing analkaline saponifylng agent and small quantities of a. salt of said agentwith an aromatic substance of Weakly acid reaction selected from thegroup consisting of phenols and carboxylic acids.

2. Process of sapom'fying filaments, threads, ribbons and like materialscomposed substantially of organic esters of cellulose comprisingtreating the same in an aqueous caustic alkali bath containing smallquantities of the salt of said alkali with a phenol.

3. Process of saponifying filaments, threads, ribbons and like materialscomposed substantially of organic esters of cellulose comprisingtreating the same in an aqueous caustic alkali bath containing smallquantities of the salt of said alkali with an aromatic carboxylic acid.

4. Process for the treatment of filaments, threads, ribbons and likematerials composed substantially of organic esters of cellulose whichcomprises subjecting the materials to substantially completesaponification by treatment with a bath containing caustic alkali andsmall quantities of a salt of said alkali with an aromatic substance ofWeakly acid reaction selected from the group consisting of phenols andcarboxylic acids.

kali and small quantities of a salt of said alkali with ordinary phenol.

6. Process of saponifying filaments, threads, ribbons and like materialscomposed substantially of cellulose acetate comprising treating the samewith a bath containing aqueous caustic alkali and small quantities of asalt of said alkali with resorcinol.

7. Process of saponifying filaments, threads, ribbons and like materialscomposed substantially of cellulose acetate comprising treating the samewith a bath containing aqueous caustic alkali and small quantities of asalt of said alkali with a phenolic carboxylic acid.

8. Process of saponifying filaments, threads, ribbons and like materialscomposed substantially of cellulose acetate comprising treating the samewith a bath containing aqueous caustic alkali and small quantities of asalt of said alkali with salicylic acid.

HENRY DREYFUS.

